Process for pre-forming orthodontic tooth bands



Sept-26,1967 R. EDILLBERG ETAL I 3,3434247 PROCESS FOR FEE-FORMING ORTHODONTIC TOOTH BANDS Filed Aug. 3, 1964 I/v VE/V TO/Q g 120 Y/V/OND E. 1) 1.455 126 FRANK R. ill/445,2

BY (LN/K 77W ATTORNEY United StatesPatent O PROCESS FOR PRE-FORMING ORTHODONTIC TOOTH BANDS Raymond E. Dillberg, Temple City, and FrankR. Miller, Bradbury, Calif., assignors to Ormco Corporation, Glendora, Calif., a corporation of California Filed Aug. 3, 1964, Ser. No. 386,881 7 Claims. (Cl. 29-160.6)

This invention relates in general to orthodontic equipment and more particularly to the method of forming a band to the proper tooth configuration, and with an externally expanded central girth area.

Orthodontia has now progressed to the stage of development wherein the doctor no longer forms his own tooth bands, but rather buys a selection of bands in various sizes and thus is able to fit a vast majority of his patients with pre-formed bands.

With the exception of the cuspid tooth, most of the teeth in the mouth of the patient are relatively uniform in cross-sectional configuration such that pre-formed bands are practical. However, a properly formed band has some particular characteristic. It is desirable to have the band formed with the central girth portion of the band expanded to a greater diameter than the opposed edges. Thus, as the band is fitted down over the patients tooth only the edge area is in contact with the tooth and thus the amount of pressure needed to form the band to the shape of the tooth is reduced.

Bands must fit relatively close to the surface of the tooth in order that the cement employed to anchor the band to the tooth may be as thin as possible. The type of cement employed for the bands is exceedingly strong in thin section, but becomes brittle and relatively easily destroyed if it is allowed to accumulate in pockets. If it is allowed to accumulate in pockets along the band edges, and later become broken away, then food juices and particles can accumulate where the cement has broken away.

The bands are made of non-corroding type of metal, and are annealed to produce a dead soft condition. Hence, as the band is driven down over the tooth, the tooth will cause the band to enlarge and conform to the shape of the tooth. The enamel will thus not be crushed or scratched by the installation of the band.

To reduce the total pressure of the band upon the tooth as it is being thus formed, the band is pre-shaped into a barrel formation with an enlarged girth portion. Thus, the gingival edge of the band is in a press fit contact with the tooth, but the girth portion generally does not make strong direct contact. Hence, the critical'edge area of the band is so closely formed to the tooth that practically no cement is needed to close up irregularities.

It has been the practice in the past to provide an expansi'ble die which has the general cross-sectional configuration of a tooth, and to place a cylindrical band around that die, and thereafter cause the die to expand. Thus, an enlarged girth portion is formed with a lesser diameter in the gingival and incisal edges. However, in actual practice, this method has met with a natural phenomena which has reduced the quality of such bands. The first stretching of the band on such a die takes place in the girth area. As the girth expands the opposed edges expand also, tending to turn under in the process, but not with a fully plastic action, and therefore the edges tend to stand away from the die. Thus, the expansion must take place to a considerable degree before the extreme edges can be caused to contact the die in the proper formation." This situation is especially prevalent in those forms wherein the gingival opening is smaller than the incisal opening.

It is an object of this invention to provide an improved ice method whereby the bands are caused to conform to the shape of the expanding die with little stretching action.

It is a further object of this invention to provide a work refinement of the metal in the critical incisal edge area in order that the metal will resist a tapping action by the doctor in seating the band upon a tooth.

As the doctor installs the 'band upon a tooth he ostensibly will use wire lugs which are placed on the sides of the band, and others placed there for the specific purpose of assisting his installation. However, there are often times when temptation and necessity will cause the doctor to tap on the actual upper edge of the band. These bands are very thin, being in the nature of from .003" to .007", and therefore will not tolerate a significant amount of edge tapping. This invention produces a grain structure which materially reduces destruction of bands from this cause.

In addition to refine-ment of the grain, the edges of the band are increased in thickness with respect to the central girth area, but without particular stretching of the girth area, and with a work hardening of the refined grain in the edge area. Therefore, another object of the invention is to work harden the edges of such band and to cause an increase in thickness.

A further object of the invention is to provide a noncircular band shape which assists in manufacturing ease and efficiency. 7

For a full understanding of the invention, a detailed description of the preferred embodiment of the process for pre-forming orthodontic tooth bands will now be given in conjunction with the accompanying drawings.

FIGURE 1 illustrates a circular blank piece of metal from which the band is constructed;

FIGURE 2 is a side elevation, partially in section, of a deep drawn cup made from the blank of FIGURE 1;

FIGURE 3 is a side elevation, partially in section, illustrating the productwhich results from removal of part of the cup bottom, the trimming of the excess flange, and the extension of the side wall by folding out the remaining portion of the bottom to produce a festoon gingival edge;

FIGURE 4 is a side view of FIGURE 3 taken from the position illustrated by the line 44 of FIGURE 3;

FIGURE 5 is a perspective view of the top edge of the band, greatly exaggerated in thickness;

FIGURE 6 is a section, greatly enlarged, through the side wall of the band;

FIGURE 7 is a schematic illustration of the use of a convex roller and concave rolling die to roll and work the side wall of the band into a barrel configuration;

FIGURE 8 is the side elevation of the band after having been worked into the barrel configuration;

FIGURE 9 is a section, greatly enlarged and exaggerated, through the wall of the barrelled configuration;

FIGURE 10 is a schematic illustration of an expansion die with a band thereon under expansion conditions; and

FIGURE 11 is a top view of a finished orthodontic tooth band. p The drawing illustrates the general manufacturing process, including the old prior art steps in band formation, and the inventive steps of formation of the band.

A 'blank metal disc 10 is drawn by conventional methods to produce a cup 12. This cup is trimmed, and a portion of the bottom wall is stamped out and removed. Thereafter the remainder of the bottom is folded out and becomes an extension of the side wall. These operations produce the seamless sleeve or band 14 having a festoon gingival edge 15 and straight incisal edge 16. Because of the natural formation caused by drawing methods, the cup 12 is thickest in the area of the top edge 18, which produces the incisal edge 16 after trimming. The bottom wall in the area of the reference character 20 is considerably thinner, and when extended to form the gingival edge 15, is considerably thinner than the top edge 16.

In prior practice a band as shown in FIGURES 1 through 5 was placed over an expansion die, such as shown in FIGURE and indicated by the reference character 22. The FIGURE 10 is not an effort to show an operative piece of equipment, but to illustrate in general principle the action of an expansion die. The object of the action of the die 22 is to form the straight wall shown in FIGURE 6 into the curved wall shown in FIGURE 9. In FIGURE 9 the girth area of the wall is of a greater diameter than the edges and 16. In FIGURE 6 a portion of the die 22 is shown in juxtaposition to the straight side wall. If this die is forced against such straight side wall the entire wall tends to expand to a greater degree. However, in view of the fact that the metal is soft and can yield to the forces, it will yield first in the girth area. Hence, a slight bowing will take place first and will increase as the expansion of the die 22 increases.

The thicker top edge 16 tends to turn to the greater degree than edge 15 and lay against the die 22. Furthermore, the die 22 generally is not as deeply curved in the area of the top edge 16 as in the area of the edge 15. In combination, therefore, these factors require a considerable amount of total expansion of the wall in order to cause both the top and bottom edges to eventually form against the side wall of the die 22.

The metal, when thus stretched to such a degree, exhibits a phenomena referred to in manufacturing parlance as orange peel. The top surface tends to break away from the metal beneath. This is a phenomena well known by metallurgists, but nonetheless requires that the band be polished to remove such orange peel surface after the expansion has taken place.

According to this invention, a two step process is employed which actually saves time and expense rather than increasing such cost, because rejects and cleaning up of the orange peel surface is eliminated, and the general objects of the invention as set forth are obtained. To carry out this two-step process, the drawing, trimming, and folding steps illustrated in FIGS. 1 through 3 are practiced to produce an initial sleeve or band 14 having a diameter approximately equal to the desired girth diameter of the finished orthodontic band. Thereafter, a mandrel or roller 24 is employed internally of the band and operates against a rollable concave die 26 to form the band to a barrel shape by deforming the end portions of the band, between its axially medial plane and its end edges, radially inward in such a way as to constrict these end portions to progressively diminishing diameter toward the end edges. See FIGURE 7. The mandrel or roller 24 has a barrel shape conforming to that of the finished orthodontic band and a girth diameter, at the medial plane of the work sleeve or band 14, approximately equal to the internal band diameter. About the periphery of the forming die 26 is a circumferentially continuous forming cavity bounded by a wall having a concave curvature in axial section which conforms to the convex curvature of the mandrel or roller in axial section.

During the present forming or barreling operation, either or both mandrel or roller 24 and the forming die 26 are driven in rotation and are simultaneously translated toward one another to urge the work sleeve or band 14 into the peripheral forming cavity in the die in such a way that the band and die turn at the same speed and in the same direction within their zone of contact. As the band enters the forming cavity, the forming die initially contacts the ends of the band and deforms these ends radially inward toward the axis of the band. Rotation of the bands with the roller brings successive circumferential portions of the band into forming contact with the die, while rotation of the die avoids relative sliding motion between the band and the forming surface of the die, i.e., the wall of the peripheral forming cavity in the die. Relative translation of the roller 24 and forming die 26 toward one another is continued until the band 14 is deformed into contact with the roller over the entire internal surface area of the band. It is now evident, therefore, that the present process is effective to inwardly deform and thereby constrict the end portions of the work hand 14 to a progressively diminishing diameter toward the end edges of the band, while the central girth portion of the band is internally supported against inward deformation by the roller 24. The roller 24 is preferably as large as convenient to assure ease in removal of the band from the die after the rolling process.

After having been rolled, the band of FIGURE 4 takes on the general appearance as shown in FIGURE 8. The rolling process is preferably one of rolling the edges inwardly, as opposed to stretching the girth outwardly, and thus the metal is not stretched thin in the girth.

The side wall shape produced by this rolling process is near the desired final configuration with respect to vertical curvature. However, the band as thus rolled does not have the necessary anatomical shape which is shown in the FIGURE 11. Hence, further formation is required. The usual means is by expansion die 22, but other means may be substituted if desired.

Inventive ingenuity is exhibited in this phase of the development. Although it was intended merely to reduce the amount of expansion required in formation of the finished band, it was then discovered that several unexpected and desirable results were obtained in addition to the one sought. First, practical manufacturing procedures provide for the barrel rolling in one area and passing of the barreled blanks to the next machine for the expansion. These orthodontic bands are quite small, being the diameter of the tooth of a child, and usually a young child. Hence, the bands are not easily handled.

Furthermore, it is necessary to place the bands on the expansion device with the festoon edge in the proper direction in order that the festoon edge will be shaped to fit the gum line of the tooth. Visual orientation takes time and is subject to error. It has been found that the irregular edge 15 will create a tendency of the bands to become oblong as they are barrelled. This shape will cause them to orient themselves all in the same direction when whirled in a centrifugal orientation device which is commonly used for sorting and aligning industrial parts. This is an advantage to the manufacturer which does not evidence itself in the finished product.

However, invention is further evidenced in that the barreling step has been found to produce a thickening of the edges 15 and 16, although there is some thinning of the girth area. By the prior methods, thinning was evidenced in the girth area but no thickening of the remote edges. This working of the material from the girth area into the edge areas has been found to produce a refined grain and a work hardened effect on the material.

As previously indicated, the doctor should not tap on the top edge of the band when it is being installed, but usually it is necessary to do so at least to some extent. Sometimes a tap too vigorous in nature will cause the band to buckle. When this happens it usually means the band must be discarded and a new one selected. This is both expensive and time-consuming. The material of the band, being in the nature of .004 when drawn, is not resistant to great force. The roll barreling has been found to produce the above described hardness and about a ten to fifteen percent increase in the thickness of the remote edges, and this increase is accompanied by a considerable increase in resistance to buckling under the tapping employed by the doctor.

The formation shown in FIGURE 8 is not a true circular form after the rolling process, as the view suggests, but is somewhat elongated as described supra. In FIG- URE 11 the top view of the finished product shows the complex nature of the band formation. Looking downwardly through the band it is seen that the gingival edge 15 is visible only in two places, because the incisal edge 16 is folded inwardly on the opposite sides. This complex form is produced by the expansion die 22, and places the band in approximately the shape necessary to fit the tooth of the patient. This is the formation desired in the final structure, and has a remnant of the barrel formation shown in FIGURE 9. The expansion, to produce the complex form of FIGURE 11 from the straight barrel formation of FIGURE 8, is considerably faster and with one of the effects of stretching and orange peel formation experienced in the prior art. This, together with the unexpected results of grain refinement, produces a new and desired product of superior quality.

While the invention has been shown and described herein in what is conceived to be a practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention which is therefore not to be limited to the details disclosed herein but is to be afforded the full scope of the invention as hereinafter claimed.

What is claimed is:

1. The method of forming a generally barrel-shaped orthodontic band which terminates in opposed incisal and gingival edges and progressively diminishes indiameter from its axially medial plane toward said edges to define a radially enlarged girth portion intermediate said edges, said method comprising the steps of:

providing a generally cylindrical, relatively thin-Walled sleeve having a diameter approximately equal to the desired girth diameter of the finished orthodontic band, and

barreling said sleeve by deforming the wall of said sleeve radially inward in the regions thereof between the axially medial plane and the ends of said sleeve to constrict said regions to progressively diminishing diameter toward said ends.

2. The method according to claim 1, including the additional step of:

supporting said sleeve against inward deformation at said medial plane thereof during said barreling step.

3. The method according to claim 1, including the additional step of:

working the material of said sleeve within said regions thereof in directions from said medial plane toward said ends of said sleeve simultaneously with said barreling step to refine the grain structure at, workharden, and thicken the ends of said sleeve.

4. The method according to claim 1, wherein:

said barreling step involves roll forming said sleeve in directions from said medial plane to said ends of the sleeve in such a way as to work the material of said sleeve within said regions thereof toward said ends of the sleeve and thereby refine the grain structure at, work-harden, and thicken said ends.

5. The method according to claim 1, wherein:

said barreling step involves supporting said sleeve on a generally barrel-shaped mandrel having a girth diameter which approximately equals the internal diameter of said sleeve, providing a circular forming die with a central axis parallel to said mandrel and a peripheral-forming cavity bounded by a wall having a concave curvature in axial section conforming to the convex surface curvature of said mandrel in axial section, producing relative translation of said mandrel and die toward one another to deform said sleeve into said cavity, and simultaneously effecting rotation of said mandrel and sleeve, and said die in opposite directions and at substantially equal speeds to bring successive circumferential portions of said sleeve into forming contact with said die, whereby said sleeve is formed to a barrel shape and the material of said sleeve is worked in directions from said medial plane toward the ends of said sleeve to refine the grain structure at, work-harden, and thicken said ends.

6. The method according to claim 1, wherein:

one end of said sleeve has an undulate edge which defines a pair of diametrically opposed arcuate crests and a pair of intervening diametrically opposed arcuate recesses and causes said sleeve to assume an oblong shape in cross section during said barrreling step, and

said method comprises the further step of providing an expansible die having an external form conforming to an optimum orthodontic band form, and placing said sleeve after barreling thereof on said die and expanding said die to deform said sleeve to said optimum form.

7. The method of forming an orthodontic band comprising the steps of:

providing a circular blank,

drawing said blank into a flanged cup having a bottom wall,

trimming the flange from said cup,

rem-oving a portion of said bottom wall to define an elongated opening in said wall extending in its lengthwise direction to the edge of said wall and diametrically opposed remaining wall portions at opposite sides of said opening,

folding out said remaining wall portions to form a cylindrical sleeve having a gingival edge at one end thereof, and

barreling said sleeve by roll forming said sleeve in directions from the axially medial plane toward the ends of said sleeve in such a way as to form said sleeve into a barrel shape and simultaneously work the material of said sleeve in directions from the axially medial plane toward the ends of said sleeve and thereby refine the grain structure at, workharden, and thicken said ends.

References Cited UNITED STATES PATENTS 1,058,669 4/1913 Goodard 72-393 1,168,212 1/1916 Hiner et a1 72-355 1,176,232 3/1916 Mauck 72-393 1,996,181 4/1935 Wait 72-111 2,301,587 11/1942 Sauer 72-111 2,790,238 4/1957 Trangmar 32-63 OTHER REFERENCES Pages 11 and 28 of Tru-Form Orthodontic Band Technique, Rocky Mountain Metal Products C0., Denver, Colo.

JOHN F. CAMPBELL, Primary Examiner.

THOMAS H. EAGER, Examiner. 

1. THE METHOD OF FORMING A GENERALLY BARREL-SHAPED ORTHODONTIC BAND WHICH TERMINATES IN OPPOSED INCISAL AND GINGIVAL EDGES AND PROGRESSIVELY DIMINISHES IN DIAMETER FROM ITS AXIALLY MEDIAL PLANE TOWARD SAID EDGES TO DEFINE A RADIALLY ENLARGED GIRTH PORTION INTERMEDIATE SAID EDGES, SAID METHOD COMPRISING THE STEPS OF: PROVIDING A GENERALLY CYLINDRICAL, RELATIVELY THIN-WALLED SLEEVE HAVING A DIAMETER APPROXIMATELY EQUAL TO THE DESIRED GIRTH DIAMETER OF THE FINISHED ORTHODONTIC BAND, AND BARRELING SAID SLEEVE BY DEFORMING THE WALL OF SAID SLEEVE RADIALLY INWARD IN THE REGIONS THEREOF BETWEEN THE AXIALLY MEDIAL PLANE AND THE ENDS OF SAID SLEEVE TO CONSTRICT SAID REGIONS TO PROGRESSIVELY DIMINISHING DIAMETER TOWARD SAID ENDS. 